Variable mercury relay



V. HOROWITZ VARIABLE MERCURY RELAY Filed Oct. 16, 1961 May 19, 1964 INVENTOR c-rorz HOEOWFT'Z ATTORNEYS United States Patent 3,133,998 VARIABLE MERCURY RELAY Victor Horowitz, Oceanside, N.Y., assignor to Ebert Electronics Corporation, Queens Village, N.Y., a cor- I poration of New York Filed Oct. 16, 1961, Ser. No. 145,129 2 Claims. (Cl. 200-412) This invention relates to mercury relays of the displacer type, and more particularly to mercury relays wherein operating characteristics may be varied according to the strength of flux applied thereto.

A difiiculty in the design of mercury relays is to provide a relay which has consistent operating characteristics over a long period of time. One of the reasons for this difiiculty in prior mercury relays having delayed make and break characteristics, is that complicated metering devices and/ or linkages are necessary to produce the delay function. In' those mercury relays utilizing delays caused by linkages such as levers, springs, wedge-shaped plugs, etc., or in those types of mercury relays utilizing the displacement and metering of not only the mercury but of a trapped gas, the ordinary wear in the parts over a period of time changes the external conditions under which the relay is operated causes inconsistencies in the operating characteristics of the relay. It is also diificult to design a versatile mercury relay having variable delayed make and break characteristics which can be mass produced and yet possess constant operating characteristics. Each relay, for example, may have a slightly different delay characteristic which may have to be compensated for in some other manner in order to produce the desired delay characteristic.

Another difliculty in the design of mercury relays is that the materials used therein may become chemically contaminated or may produce excessive eddy currents when excited by energizing coils. Such characteristics must be eliminated in order to produce a predictable contact making operation of the mercury relay.

According to the present invention there is provided, in a container preferably comprised of diamagnetic insulating material having self-lubricative properties and having a displaceable pool of mercury therein, spaced elec trodes in which said mercury pool may be displaced. There is also provided an armature buoyant in the mercury pool, in the general form of an inverted dome, said armature being comprised of two materials, one of which is magnetic for actuation by an energizing coil, and the other portion of which is of a chemically inert material having insulative properties and upon which the chemical, electrical, and electromagnetic forces have no efliect. An orifice is provided in the domed portion of the insulated portion of the displacing element in the container. The size of the orifice may be varied according to timing requirements desired. Studs'are mounted on the magnetically permeable portion of the displacing element in the container for sliding engagement with the inner walls of the container. The studs are preferably of material which is self-lubricating, such as nylon or Delrin. There are other known materials which are suitable for use in the construction of the studs and which are self-lubricating. Mounted on the ends of the mercury displacing element in the container are cushioning springs of light construction in order to protect the relay against jarring and rough handling.

In the operation of the mercury relay according to the invention, in the embodiment thereof wherein a relatively weak field is produced by the energizing coil surrounding the container, upon energization thereof, the mercury displacing element is attracted downwards, thus displacing through the orifice a quantity of mercury sufiicient to "iceupon the size of the orifice in the inverted dome of the mercury displacing element. Obviously the amount of delay in the making of contact between the spaced elec trodes may be varied by varying the size of the orifice. Upon de-energization of the electromagnetic coil, the mercury displacing element, due to its normal buoyancy in the mercury, tends to rise therein. However, the rise of the displacing element is retarded due to the restricted flow of the mercury through the orifice. Thus there is a delay in the breaking of contact in addition to delay in the making of contact. p

In the operation of the mercury relay wherein a relatively strong field is produced by an energizing coil surrounding a portion of the container, upon energization of the coil, the mercury displacing element is attracteddownwardly at a rate suificiently rapid so that most of the mercury is displaced upwardly in the space between the container and the sides of the displacing element, the orifice passing only a relatively small amount of mercury. The upwardly displaced mercury floods over the open end of the inverted dome in sutficient quantity to establish immediate making of electrical contact between the spaced electrodes. When the coil is de-energized, the mercury is metered through the orifice at a restricted rate as the displacing element rises, thereby providing a slow breaking of contact.

Of course, a relay may be provided with an energizing coil the flux of which may be varied by varying the current supplied to the coil, the flux produced thereby is varied to produce either of the operating characteristics of the relay, at will. I

Due to the self-lubricating properties of the studs mounted on the mercury displacing member and of the container, a minimum of friction between the mercury displacing element and the inside wall of'the container is maintained, thus insuring consistent operating characteristics over a long period oftime. Because the inner portion of the mercury displacing member is comprised of a chemically, electrically and electromagnetically inert material, there is no danger of corrosion or of short circuiting the spaced electrodes therein due to a mis-alignment of the mercury displacing member. Eddy currents due to the container are eliminated because of the use of non-magnetic material therefor.

It is an object of this invention to provide a mercury relay of the displacer type wherein the contact making characteristics may be varied without internal adjustment of the relay.

Another object of the invention is to provide a mercury relay of the displacer type which, responsive to a relatively strong operatingmagnetic flux, exhibits one operating characteristic, and which, responsive to a relatively weak flux, exhibits another operating characteristic.

Another object of the invention is to provide a mercury relay of the displacer type which when subjected to a relatively strong energizing field produces an immediate making and delayed breaking of contact, and which, when subjected to a relatively weak energizing field, produces delayed making and breaking of contact.

Another object of the present invention is to provide a mercury relay of the type having delayed making of contact and delayed breaking of contact with a minimum of moving parts, the susceptibility of such parts to wear or a change in chemical or electrical characteristics thereof being held to a minimum.

It is another object of the invention to provide a mercuryrela-y which eliminates eddy current eflects due to the container, material of the container having properties of being self-lubricating, non-corrosive, diamagnetic, and electrically insulating.

It is yet another object of the invention to design a mercury relay switch of the delayed make and delayed break type in which consistent operating characteristics over a long period of time are insured by providing minimum coefiicient of friction between the moving parts therein, minimizing the forces necessary to coact with said parts to pro duce the desired operating characteristics, and by providing material in the construction of the container which eliminates heating of the shell and minimizes or eliminates the effect of eddy currents in the mercury relay.

Still another object of the invention is to provide a mercury displacing element therein which is insulated from the spaced electrodes in the relay, and to eliminate the need for providing additional insulation for the container holding the pool of mercury.

These and other objects and features of the invention will be better understood by referring to the accompanying drawings in which:

FIGURE 1 is a longitudinal cross section of an embodiment of the invention; and

FIGURE 2 which is a cross sectional view of another embodiment of the invention.

Referring to FIGURE 1, a mercury relay according to the invention is shown generally at 10. Mercury relay 141 includes a container 12 made of glass, metal, hard plastic, nylon, or of nylon filled with fiberglass, the material being diamagnetic and an insulator. At one end of the container 12 are spaced electrodes 14 and 16 which are sealed in the container 12 in a known manner, for example, with epoxy, container 12 being hermetically sealed to contain inert gas or vacuum. An electromagnetic coil 18 of conventional design which may provide either a relatively strong or weak field upon energization, is located to surround a portion container 12. The field strength of coil 18 may be variable from a single source to provide a strong or weak field. Inside of the container 12 is a pool of mercury 20 contained thereby.

Inside of the container 12 is an armature plunger 22 which is buoyant in the mercury pool 20. Armature plunger 22 is actuatable by said coil to displace the mercury pool 21 so that electrical contact may be made and broken between the spaced electrodes 14 and 16. According to the invention armature plunger 22 is in the general shape of an inverted dome and has on its outside portion a tubular portion of magnetically permeable material movable in response to energization of said coil. The inner portion 26 of said armature plunger 22 is in the form of an inverted dome and is made of a ceramic or other suitable chemically, electromagnetically and electrically inert material. Studs shown at 28 are mounted on the armature portion 24 and separate the armature plunger 22 from the walls of container 12 to provide a space therebetween. The studs 28 are preferably made of a material that is self-lubricating such as, for example, nylon, or Delrin. The self-lubricating studs 28 serve the purpose of limiting the lateral movement of the armature plunger 22 in container 12, for providing a space between the plunger 22 and the container 12, and of providing for a minimum of frictional resistance between the armature plunger 22 and the walls of container 12 so that the operating characteristics of the mercury relay are less liable to change due to wear on the studs or container walls.

In the lower, domed portion of armature plunger 22 is provided an orifice indicated at 30. The orifice 30 may be drilled to be of any convenient size in order to attain the desired delay characteristics of a mercury relay 10. Alternatively, orifice 30 may be provided with threads to receive a screw plug indicated at 32, said screw plug 32 being provided with orifices of varying sizes therein depending upon the delay characteristics desired.

Cushioning springs 34 and 36 on opposite ends of the armature plunger are provided to protect the relay from shock.

In operation, upon energization of the coil 18 to produce a relatively weak electromagnetic flux, the armature plunger 22 is attracted downwardly thereby displacing a mass of mercury upwards in the container 12. However, restricted size of orifice 32 slows the rate of the displacement of mercury in the container 12, thereby causing a relatively slow downward motion of the armature plunger 22. During the travel of armature plunger 22 downward in the container 12, sufficient mercury in pool 29 will be displaced through orifice 32 into the plunger 22 to bridge the contacts between the spaced electrodes 14 and 16 for electrical contact therebetween. Upon de-energization of the coil 18, the natural buoyancy of the armature plunger 22 in the mercury pool 29 will cause it to rise in the container 12 thereby displacing the mercury 20 so that both the armature plunger and the mercury tend to return to their original positions prior to'coil energization. However, the rate of upward travel of armature plunger 22 is impeded by the restricted size of the orifice 32 which slows the rate of fiow of the pool of mercury, thereby producing a delay in the breaking of electrical contact between electrodes 14 and 16.

When a relatively strong field is produced by the coil at 18, upon energization thereof; the plunger 22 is att-racted downwardly in container 12 at a sufficiently rapid rate so that most of the mercury in pool 20 is forced upwardly through the space between the plunger 18 and the inside surface of container 12, the size of the orifice 32 being too small to pass mercury at a rate rapid enough to fill the inside of the plunger 22. Thus, the size of said space substantially governs the flow of mercury upward-1y. The mercury floods over the open end of the rapidly dropping plunger 22 in sufficient quantity to immediately bridge the electrodes 14 and 16, thereby establishing electrical contact therebetween through the mercury.

Another embodiment of the invention is shown in FIGURE 2, wherein there is provided a mercury relay in which the electrodes are located at opposite ends of the container. For convenience, those parts of the mercury relay of the invention which are similar to those of FIGURE 1 are given the same reference numerals. The mercury relay according to the invention as embodied in FIGURE 2 is shown at 38 having a container 46. -At one end of the container 4t is an electrode 42. which extends into the container and is suitably sealed therein in a known manner as for example, by using a sealing material such as epoxy. The portion of the electrode 42 extending into the container is insulated with a suitable insulating material indicated at 44, and at the lower end of electrode 42 there is provided a cup made of inert material such as, for example, alumina, which is chemically inert and non-responsive to electrical or electromagnetic forces. That portion of the electrode 42 extending into the cup is bare and is suitably connected as, for example, by bonding, fusing or other suitable means to the cup 46. Sealed into the container 40 at the other end thereof is another electrode 48, the bare end of which is in electrical contact with a pool of mercury 50 in the container 40. The top-most level of the mercury pool 50 is somewhat below that of the open end of cup 46, and is shown at 52. Sufficient mercury is placed in container 4% so that the level 52 is in a position with relation to the cup 46 so that upon a certain amount of displacement thereof due to coil energization, the mercury level 52 will exceed the open end of the cup 46 and come into contact with the bare end of electrode 42 located in the cup 46.

In the operation of the embodiment of FIGURE 2, when a relatively weak field is produced by the energization of the coil at 18, armature plunger 22 is drawn downwardly in the container 40 thereby displacing upwardly the mercury in pool 50 through the orifice 32, the orifice controlling the rate of fiow of mercury. As the armature plunger 22 travels downwardly in the container 40, sufficient mercury is displaced through metering orifice 32 in the container to reach the level of the top of the cup 46 so that electrical contact occurs through the mercury between the electrodes 42 and 48. Upon de-energization of coil 18, due to its natural buoyancy the armature plunger 22 rises in the pool of mercury 5'13. The rise of the armature plunger 22 is governed by the restricted flow of the mercury through orifice 32, and after sufficient travel thereof upwardly for a distance in container 40, sufficient mercury is displaced in the container so that the level 52 thereof is no longer in with communication with the top of the cup '46, thereby breaking the contact between the electrodes '46 and 48. It is obviously of no concern whether some mercury remains inside of the cup 4 6, because the cup is insulated from the pool of mercury.

When relatively strong field is produced by the energizing coil thereof, the plunger 22 rapidly descends in container 40, the mercury being displaced upwards primarily in the space between the side of the plunger 22 and the inside surface of container '40, only a relatively small amount of mercury passing through orifice 32 due to its restricted size in relation to the speed of moving plunger 22. The mercury floods over the open end of plunger 22 in sufficient amount to make immediate electrical contact through the mercury between the electrodes 46 and '43.

Upon de-energization of coil 13, the plunger 22, due to its buoyancy in mercury pool 50, rises in container 40. However, the speed of ascent of plunger 22 is governed by the restricted flow of mercury through orifice 32, thus providing gradual upward motion of the plunger to produce a slow breaking of electrical contact between electrodes 46 and 48.

It will be appreciated that the novel construction of the relay according to the invention, wherein the interrelated action of the elements differs depending upon applied field strcngth, permits the mass production of standard mercury relays for which only the strength of an external energizing coil need be varied in order to vary the operating characteristics of the relay.

Moreover, due to the fact that the studs 28 in frictional engagement with the walls of the container 4% are of self-lubricating material, and the fact that the material of the container itself is preferably self-lubricating the mercury relay according to the invention is capable of hard, repeated use over a long period of time Without appreciable Wear between the moving parts thereof, thereby minimizing inconsistency of operation. In addition, the self-lubricating action of the studs 2? permits the use of smaller low strength energizing coils thus reducing temperature and eddy current effects.

It is to be understood that the forms of my invention as embodied in the above exemplary illustrations, as herewith shown and described, are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangement of the parts may be resorted to without departing from the spirit of my in- WGIItlOI'l, which is limited only by the following claims.

What I claim is: y

1. In a mercury relay, an envelope, a pool of mercury in said envelope, a mercury fillable plunger in said pool of mercury, said plunger having a relatively large opening at least adjacent its top and a relatively small metering orifice at least adjacent its bottom, the height of said relatively large opening with respect to said bottom being less than the height of said pool of mercury, and a relatively large passage for said mercury extending from under said plunger to said relatively large opening, at least one contact positioned to be contacted by said mercury only when said plunger is depressed and substantially filled by said mercury, and one further contact which contacts said mercury at least whenever said one contact contacts said mercury.

2. In a mercury relay, an envelope, a pool of mercury in said envelope, a plunger in said pool of mercury, means for raising and depressing said plunger with respect to said pool of mercury at will, said plunger being a receptacle for said mercury, said receptacle including a metering orifice for slowly admitting mercury to said receptacle, means additional to said metering orifice for rapidly admitting mercury to said receptacle in response to depression of said receptacle into said pool of mercury at a rate greater than the rate at which mercury is admitted to said receptacle via said metering orifice.

References Cited in the file of this patent UNITED STATES PATENTS 2,384,423 Larson Sept. 4, 1945 2,457,681 Keating et al Dec. 28, 1948 2,973,417 McKinney Feb. 28, 1961 

1. IN A MERCURY RELAY, AN ENVELOPE, A POOL OF MERCURY IN SAID ENVELOPE, A MERCURY FILLABLE PLUNGER IN SAID POOL OF MERCURY, SAID PLUNGER HAVING A RELATIVELY LARGE OPENING AT LEAST ADJACENT ITS TOP AND A RELATIVELY SMALL METERING ORIFICE AT LEAST ADJACENT ITS BOTTOM, THE HEIGHT OF SAID RELATIVELY LARGE OPENING WITH RESPECT TO SAID BOTTOM BEING LESS THAN THE HEIGHT OF SAID POOL OF MERCURY, AND A RELATIVELY LARGE PASSAGE FOR SAID MERCURY EXTENDING FROM UNDER SAID PLUNGER TO SAID RELATIVELY LARGE OPENING, 